This grant application addresses broad Challenge Area (04): Clinical Research and specific challenge topic 04-AI-101: Develop novel methods and address key questions in mucosal immunology. The proposal draws from strong preliminary data from our laboratory documenting defects in the activation of CD8+ Tregs in vitro in patients with IBD (Crohn's disease and ulcerative colitis) and exciting new data detailing defective CD8+ Tregs ex vivo from CD mucosa (intestine). In this proposal we will characterize normal human CD8+ regulatory T cell lines (derived from the lamina propria), define their mechanism of suppression and develop approaches to expand precursors of these cells from the peripheral blood. Our preliminary data suggest that normal LP derived CD8+ Tregs are potent inhibitors of immune responses while similar lines derived from patients with Crohn's disease fail to suppress. If we can generate Treg lines from peripheral blood precursors from CD patients, we will have developed a novel cell based therapeutic for the treatment of CD. The first aim will focus on defining phenotypic and functional characteristics of normal lamina propria regulatory CD8+ T cell lines. This will include the development of monoclonal antibodies against surface molecules involved in mediating the suppressor effector function. This mAb will also allow for the identification of precursor cells in the PB. The second aim will compare and contrast LP CD8+ T cell lines from Crohn's and ulcerative colitis patients vs. normal controls. An important feature of this aim will be a microarray analysis that will not only identify specific differences in CD vs normal cell lines but also add a different perspective on the mechanism of suppression by normal lines. Finally, the third aim will focus on efforts to identify precursors of CD8+ Tregs in the PB and develop strategies to expand these cells ex vivo. The ultimate goal will be to utilize the peripheral blood derived cell lines as novel therapeutics in the treatment of IBD. Funding for these studies will allow us to hire two additional individuals (one post-doctoral fellow to perform the biochemical analysis of the cell surface molecule involved in suppressor effector function and one technician involved in the immunohistochemistry, cell sorting and analysis. The microarray studies in aim 2 will be performed at the Baylor Institute for Immunology Research where additional technicians will be required. These latter studies highlight a new alliance between Mount Sinai and the BIIR that provides enabling technologies to translate the results from these studies into novel cell based therapeutics for clinical trials. PUBLIC HEALTH RELEVANCE: Crohn's disease (CD) and ulcerative colitis (UC), the major forms of Inflammatory bowel disease (IBD), are a growing and serious health concern in the United States with reported prevalence rate as high as 43.6 per 100,000. IBD is characterized by chronic and relapsing inflammation of the gastrointestinal tract representing defects in the control of immune responses in the intestine. We believe that CD8+ regulatory cells are an important cell population involved in controlling local immune responses in the gut and propose to study this cell subset and develop tools that will allow for the use of this cell population as a potential therapy for CD.